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Old 7th February 2006, 10:37 AM   #1
hates ground loops
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Default Preamp with tone control

Hi,

Maybe this is not considered high-end, but neither my speaker(s) nor my room has a flat frequency-response.
And sometimes some tracks need more base/mid/treble, whatever.

Well...I've tried to "design" an unbalanced preamp with built-in tone control. (-> differential pair, tone control, mixing stage)

I didn't want to use inductors, so I've tried to gyrate capacitors (=transforming capacitance into inductance, inversely proportional) using FETs.
It's possible to gyrate a capacitor using tubes or op-amps. To keep up the spirit, I want to use FETs, but I don't want to diy op-amps directly (too many parts).

Simulating it with circuitmaker indicated that some of my part's values are wrong. There's no effect on the signal, I think because the FETs in the gyrating stage are not turned on. And there's no gain.

The idea is to use the balanced zen pre as a differential pair, tone control with gyrated caps instead of inductors and a simple mixing stage (mixing the pure signal with the tweaked signal).

Maybe someone can help me fix the circuit.


Yarr, Dave
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Old 7th February 2006, 08:04 PM   #2
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Here's an old one I used from 1974 which may help you.
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Old 7th February 2006, 09:48 PM   #3
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Tone controls?? That's Sacrilege!

Egads... more stuff in the signal path.

-David
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Old 8th February 2006, 12:05 AM   #4
wchick is offline wchick  United States
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I think if you cannot make the sound in good tonal balance, you will never listen to "music".

WC
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Old 8th February 2006, 04:50 PM   #5
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Yep, it's Sacrilege. And there are more parts to the signal path, I agree.

But sometimes I just can't cope with how some tracks are mixed. Some old Beastie Boys records need more base (esp. License to ill), some recordings of Dvorak (Nr.9) are, for my taste and on my system, a bit flat in the mids, Aphex Twin loves the highs,...

I want simple tone controls, embedded in a pre-amp. That is it.



Mr. Pass,

I can't figure out the value of the middle cap, is that 3F? And the bypass cap (at the transitor), is that 10F?! And what kind of transistor should I use, maybe a TIP... or MPSA..., or can i use an n-chanel FET?

Thanks a lot, Dave
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Old 12th June 2011, 08:22 PM   #6
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Anyone who buys in to that malarky that tone controls are bad, is a sucker.
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